A7-1-2: Alert on move constructor declaration that cannot be constexpr specified

[rvermeulen]

Affected rules

• A7-1-2

Description

The query alerts on a move constructor declaration outside the class body.
Per [dcl.constexpr] paragraph 1, a constexpr shall only be applied to the declaration of a function with the additional constraint that all of its declarations shall contain the constexpr. When the advice associated with the alert is followed, this results in the compilation error:

error: constexpr declaration of 'MyClass' follows non-constexpr declaration

Example

File: myclass.hpp

class MyClass {
 public:
  ...
  MyClass(MyClass&&) noexcept;
  ...
 private:
  int data;
}

File: myclass.cpp

MyClass::MyClass(MyClass&&) noexcept = default;

[lcartey]

I believe this is a reporting issue, and not a false positive. The query should report that all declarations of a function need to be changed to include constexpr. The message could be adapted as follows:

"The function " + ecef.getName() + " and all declarations could be marked as 'constexpr'."

[lcartey]

Closing as not planned as we have determined we should not report functions under this rule (#843).